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Old 08-05-10, 05:46 AM   #1
tizeye 
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Squeaking hydraulic front brakes

While I fixed the problem on my road bike, the mountain bike is giving me a hard time.

The rear brakes are fine, but the front brakes, I may as well have a horn on the handlebar letting people know I am slowing down. The squeal occurs during the rolldown with either light pressure to slow or 100% pressure applied for hard (or full stop) braking.

Checking other threads lead to the sheldon brown site. Only primary troubleshooting was headset loose. Tested an appears tight. Plus squeaky brakes occurred both before and after the LBS repaired the RocShok Tora fork under warranty for some known damper/lockout issues with that fork - and re-assembly would require tightening the headset to spec if wasn't from the factory.

These are Shimano M485 hydraulic with 160 rotors.

I've done the following: 1) after 100 or so miles, torched the pads to burn off factory shipping oil or other contamination. 2) recently light sanding the pads (how I resolved the road bike issue) after washing the bike(s). 3) periodically try cleaning the rotor with moist hand towlettes. (4) pay attention to seating when mounting the wheel making sure the rotor is not angled between the pads.

Any suggestions? I am about at the point of getting new pads despite the relativeve newness (500-1000 miles) of the pads.

Last edited by tizeye; 08-06-10 at 06:50 AM.
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Old 08-05-10, 09:04 AM   #2
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As I posted on another noisy brake posting, I had to change the pads on my Avid Juicy rear to get the noise under control. I tried most of what you noted, and added checking the rotor for trueness. I changed the pads and things were good-to-go. I'm guessing that I glazed the pads when new and nothing I did would break that glaze. Good luck.
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Old 08-05-10, 09:19 AM   #3
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Quote:
Originally Posted by tizeye View Post

I've done the following: 1) after 100 or so miles, torched the pads to burn off factory shipping oil or other contamination. 2) recently light sanding the pads (how I resolved the road bike issue) after washing the bike(s). 3) periodically try cleaning the rotor with moist hand towlettes. (4) pay attention to seating when mounting the wheel making sure the rotor is not angled between the pads.

Any suggestions? I am about at the point of getting new pads despite the relativeve newness (500-1000 miles) of the pads.
You might want to invest in new pads. Personally, I prefer the factory brand pads, rather than "aftermarket", assuming I have factory rotors. (Perhaps it's a hold out from my automotive days, but the factory brake parts seemed to work the best).
Comments to your itemized list above:

1. Torching is not necessary and may be the cause of your woes. New brake pads may squeal but with use, the pads will "burnish" themselves and begin to match the rotor contours. When you torched it, you could've caused carbon to build up or increased the hardness of the material (I'm only guessing here

2. Lightly sanding might be okay, but use of brakes might be a better way. If you are using old rotors and new pads, the pads will take time to wear to match the existing rotor surface contour. After use, rotors get circular wear lines. It'll take brake usage to wear the pads to match the wear lines. I have friends who always change pads and rotors together. It's probably overkill to change both.

3. Moist hand toweletts may be the cause of your squealing too. Those towellettes may contain moisturizers or lotions and that remain on the rotor and will change the braking surface characteristics. The recommended, best and cheapest cleaner is isopropyl (rubbing) alcohol. It'll remove contaminants and light oil, and also dries fast and leaves no residue. And pint bottle costs $1.

4. You can adjust the caliper mounts so the pads are always aligned when the wheel is dropped in. In other words, you shouldn't have to adjust the wheel mounting to align to the pads. Rather, align the caliper so the pads are automatically aligned when the wheel is mounted.

Bottom line: Assuming your rotors are not warped, clean them well with alcohol, then install new pads. Initially, the braking may not be most efficient or may squeal a bit, but after use, the squealing will go away and braking performance will increase after the pads are burnished. If you got the cash, buy a new set of rotors and start fresh.
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Old 08-05-10, 10:29 AM   #4
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Likely at this point you'll need new pads since the hand towelettes will likely have put soaps and moisturizers onto the pad linings as MudPie mentioned. Once on the pads it's very hard to get some of that stuff to go away.

A last ditch try for your case would be to remove the pads, sand off any glazing so they are dull on the face then boil them in regular water for an hour or so. While you're making the "pad soup" use some 320 wetordry silicon carbide sandpaper to scuff up both sides of the rotor braking surfaces. And don't sand "around" the rotor, you want lots of cross hatching lines. So sand in small swirls or in tangents to the rotor. Following that clean the rotor with either brake cleaner or the rubbing alchohal on paper towels. Keep flipping and using new ones until the cleaner or alchohal on the towel does not come away with any staining at all. It's not even a good idea to touch the rotors where you can help it since your finger oil can even be enough to cause a problem if there's enough of it. Install the boiled pads and try it out. At first I'm pretty sure you won't have any squeal. But as the cross hatching wears and the pad faces burnish up again the squeal may come back. If it does then you need to get new pads. And contrary to MudPie's vote for OEM pads in this case you don't want the same material over again. Go for a good aftermarket company such as EBC or Koolstop instead. Squealing is about the friction between the pad and rotor metal having a hysterysis. That is, it grabs, jumps a little than lets go for a millisecond then grabs again. It's the same effect as we see on violins or rubbing a wet finger on the rim of a wine glass. And it's caused by a particular frictional charactaristic between the pad and the rotor. Change that balance just a little and the effect goes away and you have silence. The sanding and cleaning will alter it for a while. But if it comes back then you need to alter something in a more drastic way. Hence the aftermarket brake pads.
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Old 08-05-10, 12:45 PM   #5
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I used autmotive brake cleaner to get rid of my squeal..
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Old 08-06-10, 07:06 AM   #6
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ARRGGGG!
Went to the LBS and bought new pads, wrong ones.
Bought M08 Resin pads, and on disassembly discovered had BO1S Resin pads. Further, the M08 package specifically skipped my brake model # as it listed the higher and lower number. Since the pads looked identical searched the internet to see if interchangeable. Shimano of little help as nothing on individual pads, and exploded parts list did not have an 'interchageable' notation as othe componets on the brake did.

Google search "Shimano M485 B01S" and really became interesting. Appears that squealing is common as there was a problem with that brake, with service bulletin addressing oil leakage, and the M485 (and an interim fix M486) was eventually discontinued, replaced by the M495 which uses the M08 pad. My brakes don't appear to be oil contaminated, and did appear dry.

Guess I will go back to the LBS and see what they say.
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